Ashya King was taken to the Czech Republic to receive treatment (Picture: Reuters)

Researchers said common ‘toxic’ effects of photon-based radiotherapy on the heart, lungs and stomach were not seen in those treated with proton treatment.

The study, led by Massachusetts General Hospital, said: ‘Our findings suggest that proton radiotherapy seems to result in an acceptable degree of toxicity and had similar survival outcomes to those achieved with photon-based radiotherapy.

‘Although there remain some effects of treatment on hearing, endocrine, and neurocognitive outcomes – particularly in younger patients – other late effects common in photon-treated patients, such as cardiac, pulmonary, and gastrointestinal toxic effects, were absent.’

The study analysed 59 patients aged between three and 21 from 2003 to 2009.

Some 55 of the patients had the tumour partially or completely removed through surgery, while all patients received chemotherapy as well as proton beam therapy.